Spray congealed lipid microparticles with high protein loading: Preparation and solid state characterisation

Effect of drug load and lipid-wax blends on drug release and stability from spray-congealed microparticles

This study was designed to evaluate paraffin wax as a potential controlled release matrix for spray congealing and its impact on drug release and stability of the microparticles. Paraffin wax can form a hydrophobic barrier to moisture and reduce drug degradation besides retarding drug release in the gastrointestinal tract. More hydrophilic lipid-based additives can be incorporated to modulate the drug release through the paraffin wax barrier. This study reports the findings of lipid-wax formulations at preserving the stability of moisture-sensitive drugs in spray-congealed microparticles. Aspirin-loaded microparticles formulated with different drug loads, lipid additives, and lipid:wax ratios were produced by spray congealing. Stearic acid (SA), cetyl alcohol (CA), and cetyl ester (CE) were the lipid additives studied. The microparticles were evaluated for yield, encapsulation efficiency, particle size, drug stability, and release. CE exhibited the greatest effect on increasing drug release, followed by CA and SA. Dissolution profiles showed the best fit to Weibull kinetic model. The degree of drug degradation was low, with CA imparting the least protective effect, followed by SA and CE. Paraffin wax is useful for preserving the stability of moisture-sensitive aspirin and retarding its release from spray-congealed microparticles. The addition of lipid additives modulated drug release without compromising drug stability.

Solid Lipid Microparticles for Oral Delivery of Catalase: Focus on the Protein Structural Integrity and Gastric Protection

Protein inactivation either during the production process or along the gastrointestinal tract is the major problem associated with the development of oral delivery systems for biological drugs. This work presents an evaluation of the structural integrity and the biological activity of a model protein, catalase, after its encapsulation in glyceryl trimyristate-based solid lipid microparticles (SLMs) obtained by the spray congealing technology. Circular dichroism and fluorescence spectroscopies were used to assess the integrity of catalase released from SLMs. The results confirmed that no conformational change occurred during the production process and both the secondary and tertiary structures were retained. Catalase is highly sensitive to temperature and undergoes denaturation above 60 °C; nevertheless, spray congealing allowed the retention of most biological activity due to the loading of the drug at the solid state, markedly reducing the risk of denaturation. Catalase activity after exposure to simulated gastric conditions (considering both acidic pH and the presence of gastric digestive hydrolases) ranged from 35 to 95% depending on the carrier: increasing of both the fatty acid chain length and the degree of substitution of the glyceride enhanced residual enzyme activity. SLMs allowed the protein release in a simulated intestinal environment and were not cytotoxic against HT29 cells. In conclusion, the encapsulation of proteins into SLMs by spray congealing might be a promising strategy for the formulation of nontoxic and inexpensive oral biotherapeutic products.

Analytical Techniques for the Assessment of Drug-Lipid Interactions and the Active Substance Distribution in Liquid Dispersions of Solid Lipid Microparticles (SLM) Produced de novo and Reconstituted from Spray-Dried Powders

Solid lipid microparticles (SLM) can be presented as liquid suspension or spray-dried powder. The main challenge in SLM technology is to precisely determine the location of the active substance (API) in the different compartments of the formulation and its changes during SLM processing. Therefore, the purpose of the research was to assess the distribution of the API and to investigate the nature of the API-lipid interaction when the formulation was subjected to spray drying, with an indication of the most suitable techniques for this purpose. SLM were prepared with two various lipids (Compritol or stearic acid) and two model APIs: cyclosporine (0.1% and 1% w/w) and spironolactone (0.1% and 0.5% w/w). Physicochemical characterizations of the formulations, before and after spray drying, were performed by differential scanning calorimetry (DSC), atomic force microscopy (AFM), Raman spectroscopy and nuclear magnetic resonance (NMR). The API distribution between the SLM matrix, SLM surface and the aqueous phase was determined, and the release study was performed. It was demonstrated that, in general, the spray drying did not affect the drug release and drug distribution; however, some changes were observed in the SLM with Compritol and when the API concentration was lower. Only in the SLM with stearic acid was a change in the DSC curves noted. Measurements with the AFM technique proved to be a useful method for detecting differences in the surface properties between the placebo and API-loaded SLM, while the Raman spectroscopy did not show such evident differences.

Spray congealed solid lipid microparticles as a sustained release delivery system for Gonadorelin [6-D-Phe]: Production, optimization and in vitro release behavior

Sustained release lipid microparticles for a potential veterinary application were produced by the means of spray congealing using saturated triglycerides with respective surfactants. The spray congealing process was optimized using unloaded and loaded microparticles, revealing the highest impact of the spray flow on material loss. Yield could be optimized by increasing the spray flow as well as a reduction of the melt temperature from 90 to 75 °C. For the delivery system developed in this study, a release of around 15 days was targeted. The release profile was in first hand determined with the use of model substances (aspartame and tryptophan), before incorporating the decapeptide Gonadorelin [6-D-Phe]. Release could be controlled between 2 and 28 d, which was dependent on stability of microparticles upon incubation, type and concentration of emulsifier, as well as the used triglyceride. Differential scanning calorimetry and X-ray powder diffraction confirmed the crystallization behavior of C14 and C16-triglycerides in combination with various emulsifiers in different modification without impact on release.

Production and characterization of promising β-stable seed crystals to modulate the crystallization of fat-based industrial products

Spray cooling or spray chilling is a technique for obtaining solid lipid microparticles (SLMs) within the diameter range in micrometers using low temperatures and no organic solvents. It is a low-cost technique and is easy to scale-up. The production of SLMs into β-form represents a technological challenge due to the fast crystallization given by the spray cooling system, which generally results in SLMs crystallized into the metastable polymorphic form α. This study focuses on the production and characterization of SLMs by spray cooling using hard fat soybean oil (HS) added of D-limonene or canola oil, aiming to their application as β-seed crystals into lipid systems. The β-seed crystals could turn into an alternative lipid material to be used in fat-based products that present the preferential β' crystallization, like palm oil, increasing its compatibility with cocoa butter (CB) and allowing for the development of substitutes. The obtained SLMs showed spherical geometry and no agglomeration during storage at 25 °C for up to 30 days, verified by scanning electron microscopy (SEM). The mean diameters (D₅₀) were between 150 and 200 μm and the β' and β-form, determined by X-ray diffraction (XRD), appeared immediately after the crystallization process by spray cooling using HS added of 5% D-limonene (the HS control sample presented only the α-form). The SLMs of this study demonstrated their potential use as β-seed crystals into lipid systems.

Effects of Drug Particle Size and Lipid Additives on Drug Release from Paraffin Wax Formulations Prepared by Spray Congealing Technique

Paraffin wax is a hydrophobic meltable material that can be suitably used in spray congealing to develop drug-loaded microparticles for sustained release, taste-masking or stability enhancement of drugs. However, these functional properties may be impaired if the drug particles are not completely embedded. Moreover, highly viscous melts are unsuitable for spray dispersion. In this study, the effects of drug particle size and lipid additives, namely stearic acid (SA), cetyl alcohol (CA) and cetyl esters (CE), on melt viscosity and extent of drug particles embedment were investigated. Spray congealing was conducted on the formulations, and the resultant microparticles were analysed for their size, drug content, extent of drug particles embedment and drug release. The melt viscosity increased with smaller solid inclusions while lipid additives decreased the viscosity to varying extents. The spray-congealed microparticle size was largely dependent on the viscosity. The addition of lipid additives to paraffin wax enabled more complete embedment of the drug particles. CA produced microparticles with the lowest drug release, followed by SA and CE. The addition of CA and CE enhanced the drug release and showed potential for taste-masking. Judicious choice of drug particle size and matrix materials is important for successful spray congealing to produce microparticles with the desired characteristics.

Spray congealing: a versatile technology for advanced drug-delivery systems

Spray congealing is a low cost, simple and versatile method to produce microparticles without the use of organic or aqueous solvent. This review provides a detailed picture of the pharmaceutical applications of this technology, with an overview of the spray-congealed-based drug-delivery systems. First, the basic principles and equipment of spray congealing technology are presented. Then, representative examples of the drug-delivery systems are examined and critically discussed. Emphasis is given on the role of formulation variables, together with practical considerations for formulation design. In addition, the current status of the industrial applications of this technology within the pharmaceutical field is examined. The final part points out benefits, limitations and future perspectives of this technology in drug delivery.

A new melatonin oral delivery platform based on orodispersible films containing solid lipid microparticles

An innovative delivery system for melatonin, based on the incorporation of solid lipid microparticles in orodispersible films (ODFs) made of maltodextrin, was designed and developed. Lipid microparticles at two different melatonin concentrations (10 and 20% w/w) were produced by the spray congealing technology using two different lipid carrier (tristearin and hydrogenated castor oil) and characterized in terms of size, solid state, drug loading and drug release pattern. Tristearin microparticles were discarded due to a polymorphic modification of the carrier. The incorporation of hydrogenated castor oil microparticles in ODFs by using the casting method did not alter significantly the shape and dimension of the microparticles and the mechanical properties (elasticity and strength) of the films, which remained acceptable for manufacturing and handling. The in vitro release studies performed in saliva, gastric and intestinal simulated media on ODFs containing melatonin loaded in hydrogenated castor oil microparticles revealed the possibility to combine with an immediate release of the drug and a sustained release over at least 5 h period. In conclusion, the proposed drug delivery system maintains the advantages of ODFs, i.e. the suitability to be swallowed without water, and permits the tuning of drug release according to the clinical needs by modulating the ratio of free and microencapsulated drug in the ODF.

Exploring the Nano Spray-Drying Technology as an Innovative Manufacturing Method for Solid Lipid Nanoparticle Dry Powders

To take advantage of solid-state properties, the nano spray-drying (NSD) technique was investigated as an innovative one-step method to produce solid lipid nanoparticles (SLN) in the form of a dry powder starting from a lipid/leucine O/W emulsion. Compritol was chosen as wall-forming lipid. Rapamycin (Rp) was employed as a model drug to be loaded into SLN. Based on an initial screening, Lutrol F68 was chosen as surfactant and high-shear homogenization as an emulsification method. A two-level fractional factorial design and an extended factorial design were employed to determine critical factors and best preparation conditions. Compritol concentration, L-leucine/lipid ratio, and Lutrol F68 concentration resulted critical. Best conditions granted 51% yield, 3.2 μm L-leucine/SLN particle size, and a SLN population around 150 nm. All samples showed the presence of lipid aggregates. Material loss in the emulsification step was found responsible for SLN aggregation and low yield. The almost quantitative Rp loading increased SLN population span. Replacing compritol with cetyl palmitate produced aggregation of dry powders and SLN. Overall, NSD was found a fast method to produce SLN dry powders. More insightful assessment of the emulsification step and lipid property effects will be critical to the optimization of the NSD process. Hypotheses account for direct coupling of high-pressure homogenization with NSD for future successful development of this promising manufacturing method.

Encapsulations of wild garlic (Allium ursinum L.) extract using spray congealing technology

The objective of this study was to incorporate wild garlic (A. ursinum) extract into microparticles (MPs) in order to protect its valuable active compounds and improve its oral bioavailability. For this purpose, spray congealing technology was applied and Gelucire 50/13 (Stearoyl polyoxyl-32 glycerides) was selected as MPs carrier. MPs were characterized in terms of yield, encapsulation efficiency and particle size. Differential scanning calorimetry (DSC) and Fourier-transform infrared spectroscopy (FT-IR) analysis of MPs showed the absence of chemical interactions between carrier and extract and suggested that spray congealing process did not modify nor degrade the encapsulated extract. The encapsulation into MPs led to an improvement of the extract dissolution performance as well as an enhancement in solubility of >18 fold compared to the pure extract. Additionally, MPs were stable over three months showing only a minor decrease in the content of active compounds (allicin and S-methyl methanethiosulfonate) and maintaining a good antimicrobial activity. Therefore, obtained results suggested that the encapsulation of A. ursinum extract in MPs by spray congealing is a promising approach to improve the biopharmaceutical properties of the extract, without affecting its antibacterial activity.

Spray congealed lipid microparticles for the local delivery of β-galactosidase to the small intestine

Oral local delivery of therapeutic biologics is generally limited due to the multiple obstacles of the gastrointestinal (GI) tract, mainly represented by acidic stomach pH and digestive enzymes. In the present study, spray congealing was used to prepare solid lipid microparticles (SLMs) loaded with β-galactosidase (lactase), an enzyme used for the treatment of lactose intolerance, to achieve a local drug delivery to the small intestine. Lactase was characterized in terms of activity at different pH, kinetic parameters and proteolytic degradation by digestive enzymes. Then, five lipid excipients were used to prepare unloaded SLMs, which were tested regarding lipase-induced digestion. The lipid with the best performance (glyceryl trimyristate) was used to prepare lactase-loaded SLMs. Spray congealed SLMs were spherical with very good encapsulation efficiency (>95%). The ability of the SLMs to protect the enzyme from the degradation in gastric environment was correlated with the particle size and the best formulation preserved the lactase activity up to 70%. Lactase was promptly released in simulated intestinal environment, and an in vitro positive food effect was observed. The present study demonstrated the potential of spray congealing for the preparation of solid lipid formulations able to achieve local oral delivery of a biologic drug.

Effect of Lipid Additives and Drug on the Rheological Properties of Molten Paraffin Wax, Degree of Surface Drug Coating, and Drug Release in Spray-Congealed Microparticles

Paraffin wax is potentially useful for producing spray-congealed drug-loaded microparticles with sustained-release and taste-masking properties. To date, there is little information about the effects of blending lipids with paraffin wax on the melt viscosity. In addition, drug particles may not be entirely coated by the paraffin wax matrix. In this study, drug-loaded paraffin wax microparticles were produced by spray-congealing, and the effects of lipid additives on the microparticle production were investigated. The influence of lipid additives (stearic acid, cetyl alcohol, or cetyl esters) and drug (paracetamol) on the rheological properties of paraffin wax were elucidated. Fourier transform-infrared spectroscopy was conducted to investigate the interactions between the blend constituents. Selected formulations were spray-congealed, and the microparticles produced were characterized for their size, drug content, degree of surface drug coating, and drug release. The viscosity of wax-lipid blends was found to be mostly lower than the weighted viscosity when interactions occurred between the blend constituents. Molten paraffin wax exhibited Newtonian flow, which was transformed to plastic flow by paracetamol and pseudoplastic flow by the lipid additive. The viscosity was decreased with lipid added. Compared to plain wax, wax-lipid blends produced smaller spray-congealed microparticles. Drug content remained high. Degree of surface drug coating and drug release were also higher. The lipid additives altered the rheological properties and hydrophobicity of the melt and are useful for modifying the microparticle properties.

Impact of change of matrix crystallinity and polymorphism on ovalbumin release from lipid-based implants

The objectives of this study were to prepare lipid-based implants by hot melt extrusion (HME) for the prolonged release of ovalbumin (OVA), and to relate protein release to crystallinity and polymorphic changes of the lipid matrix. Two lipids, glycerol tristearate and hydrogenated palm oil, with different composition and degree of crystallinity were studied. Solid OVA was dispersed within the lipid matrixes, which preserved its stability during extrusion. This was partially attributed to a protective effect of the lipidic matrix. The incorporation of OVA decreased the mechanical strength of the implants prepared with the more crystalline matrix, glycerol tristearate, whereas it remained comparable for the hydrogenated palm oil because of stronger physical and non-covalent interactions between the protein and this lipid. This was also the reason for the faster release of OVA from the glycerol tristearate matrix when compared to the hydrogenated palm oil (8 vs. 28 weeks). Curing induced and increased crystallinity, and changes in the release rate, especially for the more crystalline matrix. In this case, both an increase and a decrease in release, were observed depending on the tempering condition. Curing at higher temperatures induced a melt-mediated crystallization and solid state transformation of the glycerol tristearate matrix and led to rearrangements of the inner structure with the formation of larger pores, which accelerated the release. In contrast, changes in the hydrogenated palm oil under the same curing conditions were less noticeable leading to a more robust formulation, because of less polymorphic changes over time. This study helps to understand the effect of lipid matrix composition and crystallinity degree on the performance of protein-loaded implants, and to establish criteria for the selection of a lipid carrier depending on the release profile desired.

The effect of polymer coatings on physicochemical properties of spray-dried liposomes for nasal delivery of BSA

This work describes the development of spray dried polymer coated liposomes composed of soy phosphatidylcholine (SPC) and phospholipid dimyristoyl phosphatidylglycerol (DMPG) coated with alginate, chitosan or trimethyl chitosan (TMC), that are able to penetrate through the nasal mucosa and offer enhanced penetration over uncoated liposomes when delivered as a dry powder. All the liposome formulations, loaded with BSA as model antigen, were spray-dried to obtain powder size and liposome size in a suitable range for nasal delivery. Although coating resulted in some reduction in encapsulation efficiency, levels were still maintained between 60% and 69% and the structural integrity of the entrapped protein and its release characteristics were maintained. Coating with TMC gave the best product characteristics in terms of entrapment efficiency, glass transition (T(g)) and mucoadhesive strength, while penetration of nasal mucosal tissue was very encouraging when these liposomes were administered as dispersions although improved results were observed for the dry powders.